1. Field of the Invention
The present invention relates to the construction and building industries, and more specifically to a device for use in foundation construction. The device has been developed especially, but not exclusively, as a piling device (or piling machine) and the invention is herein described in that context. However, it is to be appreciated that the invention has broader application and is not limited to that particular use.
2. State of the Art
Several forms of piling devices currently exist for driving reinforced concrete and H-beam piles into the ground. These include the hammer piling device. A hammer piling device includes a hammer, which is capable of free falling onto the upper end of a pile in order to drive it into the ground. The pile is mounted in an upstanding steel support frame and is lifted upwardly within the frame via a hydraulic lifting assembly. The hydraulic lifting assembly and frame can be mounted on a truck tray. Such devices are, in relative terms, cost effective to use and mobile. Unfortunately, however, the repetitive impact of the hammer onto the upper end of the pile is extremely noisy. Hammer piling also generates a large amount of ground vibration that is unpleasant, as well as potentially causing damage to buildings and other structures in the vicinity of the piling operation.
Rather than hammering a pile into the ground, a hole can be bored into the ground to the required depth and then the pile can be placed into the hole. Such a procedure requires the use of a downwardly directed rotating bore mounted within a steel frame. A mechanical arrangement for rotating the bore is required. The bore, steel frame and associated mechanical arrangement can be mounted on the tray of a truck, such that it is easily transported.
Advantageously, boring devices tend not to generate the noise or vibrations associated with hammer piling devices. Also boring devices are effective for use in large scale piling operations. Unfortunately, however, the operating cost of boring devices is generally higher than that of hammer piling devices. Also, boring a pile hole as compared to hammer driving an equivalent pile is more time consuming. Another disadvantage of boring is that a temporary area is generally required for placing loose soil for backfilling the pile hole, if necessary. This is inconvenient in many situations.
Alternatively, a hammer piling device can be used in conjunction with a boring device. Both the hammer piling device and the boring device can be mounted on a truck tray. The boring device can be used to prebore a hole. A pile can then be placed into the hole and a hammer piling device can then be used to hammer the pile into the ground to the required depth. Advantageously, preboring the hole has been found to generate less vibration compared with the previously mentioned hammer piling device when used for the entire piling process. Unfortunately, however, preboring a hole adds to the time and cost associated with the piling process. Such arrangements are also of limited piling capacity.
Hydraulic piling devices have been developed in an effort to overcome some of the problems associated with the above-described arrangements. Hydraulic piling devices include an upstanding support frame. One or more hydraulic jacking cylinders are connected at their upper ends to the support frame and extend downwardly within the frame. The lower ends of the hydraulic cylinders include a means for engaging the upper end of the pile. Alternatively, a means is provided at the lower ends of the hydraulic cylinders for gripping around the pile. Extension of the hydraulic cylinders causes the pile to be forced into the ground. The support frame is provided with counterweights to ensure that extension of the hydraulic cylinders causes the pile to be forced into the ground, rather than causing the support frame to lift from the ground. Thus, the pile is driven into the ground not by hammering or boring, but instead by a pushing force. This provides a device that is, in relative terms, substantially free of operating noise, and which generates substantially no vibrations. As a result, these devices are often referred to as “silent piling devices.”
Unfortunately, existing silent piling machines include a number of inherent problems and/or limitations.
In instances where the hydraulic jacking cylinders act on the upper end of the pile, the height of the steel support frame must be more than double the pile length for pile installation. These support frames are considerably higher than those of hammer piling machines, and consequently include an inherent instability factor, which must be considered when installing and operating the device. Also, installation of these support frames tends to be, in relative terms, time consuming, labor intensive and, therefore, costly.
Further, once a silent piling machine is installed in place and the counterweights are fitted to the support frame, it is a very time-consuming, labor-intensive and, therefore, costly process to move the device. This potential problem is particularly evident if, during the piling process, the pile encounters a large rock or other object below the surface of the ground, thereby preventing further piling in that particular location. The portion of the pile extending from the ground prevents the device being moved to a new location, leaving the device idle. Indeed, the device remains idle until the pile portion extending from the ground is broken off. Only at this point can the device be moved to a new location.
Finally, such devices are difficult to level on uneven or sloping ground.
It would, therefore, be desirable to address at least some of the above-mentioned problems associated with existing piling and boring devices.
In particular, it would be desirable to provide a pile driving device that can be operated substantially free of hammer impact noise and vibration.
It would also be desirable to provide a device that is cost effective to manufacture and use.
It would be yet further desirable to provide a piling device having a large piling capacity, which is stable, easily maneuverable and relatively simple to level on sloping or uneven terrain.